82 A BOOK OF BIRDS 



THE GULLS 



At one time regarded as very near relatives of the Petrels, it is 

 now known that, as a matter of fact, these birds are in reality very 

 closely related to the Plovers ; and this is shown, curiously enough, 

 most strikingly in the coloration of the eggs on the one hand and 

 the skeleton on the other, though many other anatomical characters 

 afford equally positive evidence of this fact. 



Like the Petrels, and unlike the Plovers, they are web-footed. 

 But they differ from the Petrels and resemble the Plovers in having 

 slit-like instead of tubular nostrils. 



Such species as display a distinct summer dress have this change 

 confined to the coloration of the head, while many species take 

 several years to acquire their fully adult dress. 



The Herring-gull (Plate XVI. fig. i) affords a good instance 

 of those Gulls which take several years, three or more, to attain the 

 characteristic adult livery. The back of the adult in the present 

 species is of a delicate French-grey, the rest of the plumage being 

 pure white, set off by the yellow colour of the feet and beak, which 

 last is further decorated by a touch of bright red. The eye, too, is 

 of a beautiful straw-yellow colour, set in a frame of vermilion 

 formed by the rim of the eyelid. The sexes cannot be distinguished 

 externally, and there is no "summer" and *' winter " dress. The 

 young birds are mottled with brown, and do not acquire their full 

 plumage until the fifth year. 



The Herring-gull is a common British bird, breeding on the 

 precipitous ledges of cliffs or on the ground. In North America 

 it has taken to breeding in trees to escape the raids of fishermen. 



Nearly allied to the Herring-gull is the Great Black-backed Gull, 

 a rather larger bird than the Herring-gull, and distinguished there- 

 from by having a dark, slaty-black, instead of a pale French-grey 

 back. 



The Common Gull and the Kittiwake (Plate XVI. figs. 2, 3) 

 are to be met with in plenty around the shores of Great Britain. 

 They have no decisive difference of plumage, nor any seasonal changes, 

 except that, in the winter, like the Herring-gull, the head and upper 



